The present invention relates to a self-adjusting rotating joint, particularly for distribution devices of liquids under pressure, of the pulse sprinkler or similar type, with all the features mentioned in the preamble of the main claim.
The rotating irrigators of the above mentioned type, with continuous or discontinuous operation, can be used in agriculture, for example to irrigate crops or surfaces of various dimensions, or in industry, for dust cloud laying or to humidify, cool down or treat material extracted from mines. Depending on the use, liquids distributed can be of various types, for example pure water, sea water, saline or acid solutions.
Such irrigators may have large dimensions and may be mounted on mobile or fixed irrigation systems. The pressurised liquid is distributed through a nozzle which is connected to the feeding duct of the liquid by means of a rotating joint. Such joint comprises bearings allowing the nozzle to pivot on a full circumference about the axis of the joint, or for a circular sector if the plant or irrigation system so requires, to have the most uniform distribution of the liquid or to avoid spraying of buildings, roads, persons or other kind of obstacles.
On the body of the nozzle, means are provided to crush the jet and to move the nozzle with continuous or stepwise rotation. Because of the strong forces generated by the jet reaction, such joints must be able to transfer high torque. Moreover, to prevent an uncontrolled rotation of the nozzle, the joint is provided with appropriate brake means to resist the moment causing nozzle rotation. Such means exert their braking action at various pressure levels of the liquid flowing in the duct. In this manner the effect of the irrigation is improved, and a more uniform and diffused distribution of the liquid on the surface to be sprinkled or on the cultivation to be irrigated is achieved.
There are known irrigators of the type described above which can support high pressures and are provided with braking means to ensure a sprinkler rotation as constant and controlled as possible.
U.S. Pat. No. 4,231,522 discloses a stepwise rotating sprinkler provided with a jet deflection system which transmits also the necessary torque to produce jet rotation. In this sprinkler there are also provided braking means ensuring nozzle rotation at substantially constant angular velocity both when the pressure of the irrigation water is rather elevated, that is at full capacity operation, and when the pressure is comparatively low, for example during the system starting phase, when the liquid feeding pump has not reached the steady state or operates at a reduced pressure for other reasons.
In such sprinkler it is necessary to provide for a structural element which has the function of transferring the high forces produced by the jet. This element joins the two parts of the rotating joint moving with relative motion and has both the function of transmitting the torque generated by jet reaction and that of being an interaction surface for the braking elements.
A first disadvantage of this known sprinkler is that the structural element connecting the two parts of the rotating joint is rather difficult to make because it must be submitted to a rather high number of machining operations starting from a single piece, which is a rather difficult and costly operation.
Moreover the complex shape of this piece is such as to cause an excessive scrap of material during the manufacture. In addition, since such element must be water tight in the contact zone with the packing and the bearing placed around it, it must have an accurate surface finish. Generally such pieces require very fine and accurate working of the surface with a machine tool and subsequently their surface must be hardened or chrome-plated to guarantee maximum resistance against oxidation and abrasive action of the liquid.
In the sealing zone between bearing and tubular element, it is necessary to provide for as small as possible a clearance between the moving parts to guarantee a perfect water tightness of the lip seal, as liquid leakage can produce in the long run oxidation, or even corrosion in other elements of the joint hampering correct operation thereof. The liquid to be sprayed generally contains many impurities that can sometimes seep in the contact zones between the two elements which rotate relatively to each other and can damage the surface of the bearing and that of the chrome-plated metal element.
It has also been proposed to use sprinklers with rotating joints characterised by high mechanical resistance to counter the torque acting on the joint itself when the sprinkler is in operation. A solution of this kind is described in EP-B-630689 disclosing a rotating joint for sprinkler, provided with braking means and with high flexural resistance to bending caused by jet reaction. However such joint presents a remarkable complexity, as the various parts from which it is formed have complex shapes and are thus expensive to manufacture.
It is an object of the present invention to overcome the above mentioned drawbacks by providing a self-adjusting rotating joint for liquid distribution, in particular for irrigation, which has a simplified structure, is easy to produce, has high effectiveness and low cost.
Another object of the invention is to provide a self adjusting rotating joint with a high flexural stiffness against the jet reaction force.
It is a further object of the invention to provide a lighter joint compared to known sprinkler joints.
Another object of the invention is to provide a rotating joint with no need for maintenance during long periods.
Another object of the present invention is to provide a rotating joint having a simplified structure such as to allow easy assembling and disassembling for spare part substitution and providing high reliability.
These objects and other that will become apparent hereinafter are achieved by a rotating joint as defined in the attached claim 1.